Cytosolic acetyl-coenzyme A (Ac-CoA), a central precursor for lipid synthesis, is primarily made from mitochondria-derived citrate by ATP-citrate lyase (ACL) in cells with sufficient nutrients. Alternatively, cytosolic Ac-CoA can be made from acetate by acetyl-CoA synthetase 1 (AceCS1) under fasting conditions. In normal cells, acetate cannot be directly produced from glucose metabolism and ACL is the primary enzyme to synthesize cytosolic Ac-CoA. Previous studies show that HCMV infection dramatically increases glycolysis in the host cells; however, most glucose carbon exits the mitochondria and is used for lipid synthesis to support viral envelope formation, rather than being oxidized to produce energy through the tricarboxylic acid (TCA) cycle. Our preliminary studies show that lipid synthesis is independent of ACL in HCMV-infected human fibroblasts, this differs from that in uninfected cells which are ACL-dependent, indicating that HCMV alters cellular metabolic pathways to generate cytosolic Ac-CoA by using acetate to support lipid synthesis. We hypothesize that HCMV activates mitochondrial acetyl-CoA hydrolase (ACH) to produce acetate from pyruvate-derived Ac-CoA. The specific aims are: 1. Determine acetate production and the carbon fluxes to acetate during HCMV infection; 2. Determine mitochondrial ACH activity, activation during HCMV infection, and its role in acetate production and HCMV-induced lipogenesis; 3. Determine the role of AceCS1 in lipogenesis induced by HCMV infection. Accomplishment of the aims will open a new area of metabolic study and create new metabolic concepts.